On March 19, a bomb ripped through Istanbul's Istiklal Street, the city's Champs-Élysées, and the second such attack on the cosmopolitan city since January. Three days later, coordinated bomb attacks struck Brussels: At 8 a.m., a bomb believed to be hidden in luggage exploded in the departure terminal at Brussels Airport, followed, minutes later, by another blast; at 9:11 a.m., a third bomb tore through a subway train as it was leaving Maelbeek station.

In the wake of such tragedy, questions follow: Why did this happen? How, if anything, could this have been prevented? What events preceded this? And while there are rarely, if ever, clear answers in instances such as these, looking at the locations themselves is a strong start.

Why Brussels

At least 30 people were killed and more than 200 injured in the coordinated attacks in Brussels’s airport and Maelbeek metro station. The Islamic State, also known as ISIS or ISIL, has claimed responsibility for the attacks, which come five days after Salah Abdeslam, the main fugitive in the Paris attacks, was captured in Brussels.

Brussels, home to the headquarters of the European Union (essentially, its capital), is veritably cosmopolitan: The area of the metro bombing, the so-called European Quarter, comprises the the European Parliament complex, EU permanent representations, embassies, industrial associations, and the offices of several NGOs, all of which daily bring in people from Europe—and beyond. Yet in the past, the city has struggled to manage and monitor neighborhoods linked to terrorism: Belgium’s home affairs minister said in November that the government does not “have control of the situation in Molenbeek,” an inner-city suburb portrayed as a jihadist breeding ground. According to a United Nations report, Belgium has per capita the highest number of citizens in Europe traveling to fight in places such as in Syria and Iraq.

After the Paris attacks, Belgian Interior Minister Jan Jambon pledged to “clean up Molenbeek,” but the politics of it aren’t so simple: Though it has just 11 million residents, Belgium also has three official languages, and Brussels alone is administered as 19 separate municipalities. With more than 100 nationalities living in less than half a square mile (and with 75 percent of its citizens from immigrant backgrounds) it is one of the world's most diverse capitals. This means, nevertheless, that fractured state structures—and divisions over language, region, and communities—make it difficult to push forth agendas that balance both ideological and linguistic concerns, however security-forward they may be. In short? Change is slow, because it requires a lot of cooperation.

Why Istanbul

A Saturday attack on Istiklal Street, Istanbul's most popular shopping district, killed five and injured more than 30 when a suicide bomber detonated the blast. In the past year, the country has seen similar attacks: It is the fourth such bombing in Turkey this year and the second one by Islamist militants. One of the most well-documented came in January, when a suicide bomber blew himself up in Istanbul's Sultanahmet Square, a popular tourist destination and shopping hub.

The nexus between Europe and the Middle East, Turkey is a liberal, secular, and progressive country with a Muslim-majority population. It is engaged in two primary battles: fighting the Islamic State in neighboring Syria and Iraq as part of a U.S.-led coalition, and battling Kurdish militants in its southeast, where the collapse of a two-and-a-half year ceasefire has led to the worst violence in the region since the 1990s. Recent car bomb attacks in the capital of Ankara killed a total of 66 people, and an offshoot of the militant Kurdistan Workers Party (PKK), which seeks to become an independent state in Turkey, claimed responsibility. Thus, the country is seemingly caught between two battles it cannot win at once.

Why Now

After Abdeslam, the Paris attack suspect, was arrested in Brussels last Friday, Belgian authorities warned that he was planning attacks in Brussels. Investigators now believe that Abdeslam was supposed to be part of the coordinated series of bombings in Brussels, and that the ISIS cell accelerated the plan when Abdeslam's hideout was discovered.

Turkey had heightened security in the run-up to the Kurdish spring festival of Newroz, on March 21, but the explosion on one of the city's main thoroughfares continued the attack on the country's commercial heart. Until recently, though most attacks had been politically focused, some of the latest assaults have targeted tourist destinations to—most likely—get more attention. Since March 17, the U.S. Department of State has warned travelers to Turkey to avoid large crowds at tourist destinations.